fix use of deprecated members in ffi samples

Change-Id: Ia0b38bfbdc3c2fe9747d024d05364c8aed4b1909
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/349580
Commit-Queue: Alexander Aprelev <aam@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
Auto-Submit: Jake Macdonald <jakemac@google.com>

samples/ffi/resource_management/arena_sample.dart

@@ -25,7 +25,7 @@ main() async {
   using((Arena arena) {
     final p = arena<Int64>(2);
     p[0] = 24;
-    MemMove(p.elementAt(1).cast<Void>(), p.cast<Void>(), sizeOf<Int64>());
+    MemMove((p + 1).cast<Void>(), p.cast<Void>(), sizeOf<Int64>());
     print(p[1]);
     Expect.equals(24, p[1]);
   });
@@ -35,7 +35,7 @@ main() async {
     using((Arena arena) {
       final p = arena<Int64>(2);
       p[0] = 25;
-      MemMove(p.elementAt(1).cast<Void>(), p.cast<Void>(), 8);
+      MemMove((p + 1).cast<Void>(), p.cast<Void>(), 8);
       print(p[1]);
       Expect.equals(25, p[1]);
       throw Exception("Some random exception");

samples/ffi/resource_management/arena_zoned_sample.dart

@@ -24,7 +24,7 @@ main() async {
   withZoneArena(() {
     final p = zoneArena<Int64>(2);
     p[0] = 24;
-    MemMove(p.elementAt(1).cast<Void>(), p.cast<Void>(), sizeOf<Int64>());
+    MemMove((p + 1).cast<Void>(), p.cast<Void>(), sizeOf<Int64>());
     print(p[1]);
     Expect.equals(24, p[1]);
   });
@@ -34,7 +34,7 @@ main() async {
     withZoneArena(() {
       final p = zoneArena<Int64>(2);
       p[0] = 25;
-      MemMove(p.elementAt(1).cast<Void>(), p.cast<Void>(), 8);
+      MemMove((p + 1).cast<Void>(), p.cast<Void>(), 8);
       print(p[1]);
       Expect.equals(25, p[1]);
       throw Exception("Some random exception");

samples/ffi/resource_management/unmanaged_sample.dart

@@ -25,7 +25,7 @@ main() {
   // For automatic management use a Arena.
   final p = calloc<Int64>(2);
   p[0] = 24;
-  memMove(p.elementAt(1).cast<Void>(), p.cast<Void>(), sizeOf<Int64>());
+  memMove((p + 1).cast<Void>(), p.cast<Void>(), sizeOf<Int64>());
   print(p[1]);
   Expect.equals(24, p[1]);
   calloc.free(p);

samples/ffi/sample_ffi_data.dart

@@ -71,7 +71,7 @@ main() {
     Pointer<Int32> p2 = p1.cast();
     print('${p2.runtimeType} value: ${p2.value}'); // -1
 
-    Pointer<Int32> p3 = p2.elementAt(1);
+    Pointer<Int32> p3 = p2 + 1;
     print('${p3.runtimeType} value: ${p3.value}'); // 2^31 - 1
 
     calloc.free(p1);
@@ -81,10 +81,10 @@ main() {
     // Data can be tightly packed in memory.
     Pointer<Int8> p = calloc(8);
     for (var i in [0, 1, 2, 3, 4, 5, 6, 7]) {
-      p.elementAt(i).value = i * 3;
+      (p + i).value = i * 3;
     }
     for (var i in [0, 1, 2, 3, 4, 5, 6, 7]) {
-      print('p.elementAt($i) value: ${p.elementAt(i).value}');
+      print('p.elementAt($i) value: ${(p + i).value}');
     }
     calloc.free(p);
   }

samples/ffi/sample_ffi_functions.dart

@@ -197,7 +197,7 @@ main() {
     Pointer<Int64> p2 = calloc(2);
     p2.value = 42;
     p2[1] = 1000;
-    print(p2.elementAt(1).address.toRadixString(16));
+    print((p2 + 1).address.toRadixString(16));
     print(p2[1]);
     Pointer<Int64> result = assign1337Index1(p2);
     print(p2[1]);

samples/ffi/sample_ffi_functions_structs.dart

@@ -50,8 +50,8 @@ main() {
     NativeCoordinateOp f1 = p1.asFunction();
 
     Pointer<Coordinate> c1 = calloc<Coordinate>(3);
-    Pointer<Coordinate> c2 = c1.elementAt(1);
-    Pointer<Coordinate> c3 = c1.elementAt(2);
+    Pointer<Coordinate> c2 = c1 + 1;
+    Pointer<Coordinate> c3 = c1 + 2;
     c1.ref.x = 10.0;
     c1.ref.y = 10.0;
     c1.ref.next = c3;

samples/ffi/sample_ffi_structs.dart

@@ -40,8 +40,8 @@ main() {
   {
     // Allocates coordinates consecutively in c memory.
     Pointer<Coordinate> c1 = calloc<Coordinate>(3);
-    Pointer<Coordinate> c2 = c1.elementAt(1);
-    Pointer<Coordinate> c3 = c1.elementAt(2);
+    Pointer<Coordinate> c2 = c1 + 1;
+    Pointer<Coordinate> c3 = c1 + 2;
     c1.ref.x = 10.0;
     c1.ref.y = 10.0;
     c1.ref.next = c3;